In an alkylation process, complex saturated hydrocarbon molecules are formed by direct union of a saturated hydrocarbon molecule and an unsaturated hydrocarbon molecule. For example, light compounds such as isobutane and butylene are converted into heavier compounds through the control of temperature and pressure in the presence of an acid catalyst. Hydrofluoric acid is presently widely used as an alkylation catalyst.
Some undesirable aromatic compounds such as, for example, heavily substituted aromatic compounds, wherein each of the alkyl groups has about 3 to about 9 carbon atoms per alkyl group, are also produced in an alkylation process. When the alkylation products are used in household products, food-related applications, cosmetics, and lantern fuel, it is generally required that they be substantially free of any aromatic compounds. The concentration of aromatic compounds can generally be reduced to 0.03 weight % or higher by a hydrotreatment process using commercially available nickel catalysts. However, reduction of aromatic compounds to less than 0.03 weight % by such hydrotreatment has never been achieved with commercially available catalysts. Therefore, a more active catalyst is required to substantially reduce the content of aromatic compounds, especially from the heavy end of the alkylate fraction. It is also highly desirable to develop a new catalyst that can substantially reduce the concentration of the undesirable aromatic compounds.
Furthermore, sulfur or sulfur-containing compounds may be present in refining processes and potentially could be present in an alkylation process. Commercially available catalysts used in removing or reducing the aromatic compounds are normally prone to sulfur poisoning. Therefore, it appears there is an ever-increasing need to develop a catalyst which is not sensitive to sulfur or sulfur-containing compounds and still can substantially reduce the concentration of the undesirable aromatic compounds.